package bigdata.mapreduce;

import java.io.IOException;
import java.util.Iterator;
import java.util.StringTokenizer;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Job;
import org.apache.hadoop.mapreduce.Mapper;
import org.apache.hadoop.mapreduce.Reducer;
import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;
import org.apache.hadoop.util.GenericOptionsParser;

public class WordCount {
	
	public WordCount() {}
	
	public static class TokenizerMapper extends Mapper<Object,Text,Text,IntWritable>{
		private static final IntWritable one=new IntWritable(1);
		private Text word=new Text();
		public TokenizerMapper() {}
		
		@Override
		public void map(Object key,Text value, Context context) throws IOException,InterruptedException{
			StringTokenizer itr=new StringTokenizer(value.toString());
			while(itr.hasMoreTokens()) {
				this.word.set(itr.nextToken());
				context.write(this.word,one);
			}
		}
	}
	
	public static class IntSumReducer extends Reducer<Text,IntWritable,Text,IntWritable>{
		private IntWritable result=new IntWritable();
		public IntSumReducer() {}
		
		@Override
		public void reduce(Text key,Iterable<IntWritable> values,Context context)
		throws IOException, InterruptedException{
			int sum=0;
			IntWritable val;
			for(Iterator<IntWritable> i$=values.iterator();i$.hasNext();sum+=val.get()) {
				val=(IntWritable)i$.next();
			}
			this.result.set(sum);
			context.write(key, this.result);
		}
	}	

	public static void main(String[] args) throws IOException, ClassNotFoundException, InterruptedException {
		// TODO Auto-generated method stub
		Configuration conf=new Configuration();
		String[] otherArgs=(new GenericOptionsParser(conf,args)).getRemainingArgs();
		if(otherArgs.length<2) {
			System.err.println("Usage:WordCount<in>[<in>...] <out>");
			System.exit(2);
		}
//		else {
//			for(int i=0;i<otherArgs.length;i++) {
//				System.out.println(otherArgs[i].toString());			
//			}
//			System.out.println(WordCount.class.toString());
//			System.exit(0);
//		}
		
		
		Job job=Job.getInstance(conf,"WordCount");
		job.setJarByClass(WordCount.class);
		
		job.setMapperClass(WordCount.TokenizerMapper.class);
		job.setReducerClass(WordCount.IntSumReducer.class);
		
		job.setMapOutputKeyClass(Text.class);
		job.setMapOutputValueClass(IntWritable.class);
		
		job.setOutputKeyClass(Text.class);
		job.setOutputValueClass(IntWritable.class);
		
		for(int i=0;i<otherArgs.length-1;i++) {
			FileInputFormat.addInputPath(job, new Path(otherArgs[i]));			
		}
		
		FileOutputFormat.setOutputPath(job, new Path(otherArgs[otherArgs.length-1]));
		System.exit(job.waitForCompletion(true)?0:1);		
	}
}
